2026 ADU
Permit Fees.
What the city actually charges to permit a detached ADU in 2026 — plan review, building permit, school impact, and utility hookup. Pulled from published city fee schedules for a 900 sq ft DADU at $180K–220K declared value.
Permit fees by city
| City | Plan review | Building permit | School impact | Utility hookup | Total est. |
|---|---|---|---|---|---|
| Seattle SDCI 2026 fee schedule | $2,400 | $4,800 | $0 (exempt) | $3,200–6,500 | $10,400–13,700 |
| Bellevue Bellevue Dev Svcs 2026 | $1,950 | $4,100 | $2,800 (50% of SF) | $4,500–8,000 | $13,350–16,850 |
| Tacoma Tacoma PDS 2026 | $1,650 | $3,400 | $1,950 (50% of SF) | $3,800–6,200 | $10,800–13,200 |
| Kirkland Kirkland Planning 2026 | $2,100 | $4,300 | $3,100 (50% of SF) | $4,200–7,500 | $13,700–17,000 |
| Redmond Redmond PWP 2026 | $2,050 | $4,200 | $2,950 (50% of SF) | $4,000–7,200 | $13,200–16,400 |
| Renton Renton CED 2026 | $1,800 | $3,700 | $2,400 (50% of SF) | $3,900–6,800 | $11,800–14,700 |
| Sammamish Sammamish Comm Dev 2026 | $2,200 | $4,400 | $3,400 (50% of SF) | $5,500–9,000 | $15,500–19,000 |
| Issaquah Issaquah Dev Svcs 2026 | $2,100 | $4,250 | $3,200 (50% of SF) | $5,200–8,500 | $14,750–18,050 |
| Mercer Island MI CPD 2026 | $2,400 | $4,700 | $3,600 (50% of SF) | $5,800–9,500 | $16,500–20,200 |
| Everett Everett Planning 2026 | $1,750 | $3,600 | $2,200 (50% of SF) | $3,700–6,400 | $11,250–13,950 |
| Edmonds Edmonds Dev Svcs 2026 | $1,900 | $3,900 | $2,650 (50% of SF) | $4,100–7,000 | $12,550–15,450 |
| Shoreline Shoreline PCD 2026 | $1,850 | $3,800 | $2,500 (50% of SF) | $4,000–6,800 | $12,150–14,950 |
| Bothell Bothell Comm Dev 2026 | $1,900 | $3,900 | $2,700 (50% of SF) | $4,200–7,100 | $12,700–15,600 |
| Auburn Auburn Comm Dev 2026 | $1,600 | $3,300 | $1,800 (50% of SF) | $3,500–5,900 | $10,200–12,600 |
| Kent Kent ECD 2026 | $1,650 | $3,400 | $1,900 (50% of SF) | $3,600–6,100 | $10,550–13,050 |
| Federal Way FW Comm Dev 2026 | $1,600 | $3,300 | $1,750 (50% of SF) | $3,400–5,800 | $10,050–12,450 |
Methodology: Representative 900 sq ft detached ADU with $180–220K declared construction value, standard utility runs (<100 ft to mains), no critical-area surcharges. Verify with the current city fee schedule before applying — fees adjust annually on January 1.
Reading the line items
- Plan review
- Charged when you submit your permit application. Covers structural, energy, mechanical, and zoning review. Larger ADUs and complex sites (steep slopes, critical areas) trigger surcharges of 15–40%.
- Building permit
- Calculated as a percentage of declared construction value (typically 0.8–1.4%). The fees above assume a $180K–220K project. Inspection fees are usually bundled.
- School impact fees
- Capped by RCW 36.70A.681 at 50% of single-family rate as of HB 1337 (2023). Exempt in Seattle. Highest in Sammamish, Issaquah, Mercer Island (Issaquah/Bellevue school districts).
- Utility hookups
- Water + sewer + power + gas. Highest variability — depends on distance to mains, meter size, and whether the ADU shares connections with the main house. Side sewer permits add $400–900.
- Not included
- Architect/engineer fees ($8–18K), surveys ($1.5–3K), geotechnical reports ($2.5–6K), demolition permits ($300–1,200), and traffic mitigation in select cities.
Frequently asked
Why are Seattle's total fees often the lowest in the region?+
Seattle exempts ADUs from school impact fees entirely (since 2019), and Seattle Public Utilities has standardized connection fees. The plan review fee is higher than the suburbs, but the elimination of $2,000–4,000 in school impact fees more than offsets it.
Are these fees set in stone?+
No — Puget Sound cities publish fee schedules annually, usually adjusted for CPI on January 1. The numbers above reflect 2026 schedules in effect as of January. Always verify with the city's current fee schedule before applying.
What's the cheapest Puget Sound city for ADU permit fees?+
Auburn, Federal Way, Kent, and Tacoma cluster at the low end — typically $10K–13K all-in for a 900 sq ft DADU. Eastside cities (Bellevue, Kirkland, Sammamish, Mercer Island) run 30–80% higher, mostly due to school impact fees and higher utility connection costs.
Can permit fees be financed?+
Yes — construction loans, HELOCs, and most ADU-specific lenders allow permit fees in the soft cost budget. Some cities also defer impact fees until certificate of occupancy.
What's the difference between a permit fee and a tap fee?+
Permit fees are paid to the city for review and inspection. Tap fees (also called system development charges) are paid to the water/sewer utility for the right to connect to the public system. Both are usually owed before the ADU can be occupied.
City fee schedules & statutes
- Source ↗Seattle SDCI Fee SchedulePlan review + building permit
- Source ↗Bellevue Development Services FeesAnnual fee schedule
- Source ↗Tacoma Planning & Development FeesPermit & impact fees
- Source ↗Kirkland Planning FeesCity fee schedule
- Source ↗King County School Impact FeesPierce/King school districts
- Source ↗RCW 36.70A.681 — ADU impact fee cap50% cap statute
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